Abstract: By means of TEM, HRTEM, XRD, XPS and TPO methods, structure and properties of the carbon-nanofibers formed catalytically from decomposition of CH₄ or CO have been investigated. The TEM observation shows that these materials are even nanotubes with the outer diameters of 15～20 nm. Their XRD patterns are very close to that of graphite, but the XRD features are somewhat broadened, indicating that the degree of long-range order of these nanostructures is relatively low in comparison with that of graphite. HRTEM observation reveals that the wall of these nanotubes is constructed by many layers of carbon with graphite-like platelets in an extremely ordered arrangement, with the orientation of the conical graphite like platelets inclined to the central axis of the tube for the material produced from CH₄ and the cylindrical graphite-like platelets parallel to the tube axis for that from CO, respectively. XPS measurements show that C_1s electron binding energy in these carbon nanotubes is about 0.5 eVlower than that of graphite. The results of the O₂-TPO testing demonstrate that content of amorphous carbon in these materials is very low, and then the nanostructures are entirely graphitic in nature; the TPOresults also show that the temperature for gasification of the material produced from CH₄ is about 100 Khigher than that from CO, indicating that the former has a better oxygen-resistibility than the latter.

Key words: Carbon-nanotube, Carbon-nanostructure, Catalytic decomposition, CH₄, CO